This invention relates generally to refrigerated beverage and food service merchandisers and, more particularly, to a foul resistant condenser coil therefor.
It is long been the practice to sell soda and other soft drinks by way of vending machines or coin operated refrigerated containers for dispensing single bottles of beverages. These machines are generally stand alone machines that are plugged into standard outlets and include their own individual refrigeration circuit with both evaporator and condenser coils.
This self serve approach has now been expanded to include other types of “plug in” beverage and food merchandisers that are located in convenience stores, delicatessens, supermarkets and other retail establishments.
In such stores, cold beverages, such as soft drinks, beer, wine coolers, etc. are commonly displayed in refrigerated merchandisers for self-service purchase by customers. Conventional merchandisers of this type usually comprise a refrigerated, insulated enclosure defining a refrigerated product display cabinet and having one or more glass doors. The beverage product, typically in cans or bottles, single or in six-packs, is stored on shelves within the refrigerated display cabinet. To purchase a beverage, the customer opens one of the doors and reaches into the refrigerated cabinet to retrieve the desired product from the shelf.
Beverage merchandisers of this type necessarily include a refrigeration system for providing the cooled environment within the refrigerated display cabinet. Such refrigeration systems include an evaporator coil housed within the insulated enclosure defining the refrigerated display cabinet and a condenser coil and compressor housed in a compartment separate from and exteriorly of the insulated enclosure. Cold liquid refrigerant is circulated through the evaporator coil to cool the air within the refrigerated display cabinet. As a result of heat transfer between the air and the refrigerant passing in heat exchange relationship in the evaporator coil, the liquid refrigerant evaporates and leaves the evaporator coil as a vapor. The vapor phase refrigerant is then compressed in the compressor coil to a high pressure, as well as being heated to a higher temperature as a result of the compression process. The hot, high pressure vapor is then circulated through the condenser coil wherein it passes in heat exchange relationship with ambient air drawn or blown across through the condenser coil by a fan disposed in operative association with the condenser coil. As a result, the refrigerant is cooled and condensed back to the liquid phase and then passed through an expansion device which reduces both the pressure and the temperature of the liquid refrigerant before it is circulated back to the evaporator coil.
In conventional practice, the condenser coil comprises a plurality of tubes with fins extending across the flow path of the ambient air stream being drawn or blown through the condenser coil. A fan, disposed in operative association with the condenser coil, passes ambient air from the local environment through the condenser coil. U.S. Pat. No. 3,462,966 discloses a refrigerated glass door merchandiser having a condenser coil with staggered rows of finned tubes and an associated fan disposed upstream of the condenser coil that blows air across the condenser tubes. U.S. Pat. No. 4,977,754 discloses a refrigerated glass door merchandiser having a condenser coil with in-line finned tube rows and an associated fan disposed downstream of the condenser that draws air across the condenser tubes.
One problem that occurs with such self-contained merchandisers is that they are often in area that is heavily trafficked by people that tend to track in debris and dirt from the outside. This, in turn, tends to expose the condenser coil, which is necessarily exposed to the flow of air in the immediate vicinity, to be susceptible to airside fouling. With such fouling, the accumulation of dust, dirt and oils impede refrigeration performance. As the condenser coil fouls, the compressor refrigerant pressure rises, which leads to system inefficiencies and possibly compressor failure. Further, such products are often used in locations where periodic cleaning is not likely to occur.
The usual structure for such a condenser coil is a tube and fin design wherein a plurality of serpentine tubes with refrigerant flowing therein are surrounded by orthogonally extending fins over which the cooling air is made to flow by way of a fan. Generally, the greater the tube and fin densities, the more efficient the performance of the coil in cooling the refrigerant. However, the greater the tube and fin densities, the more susceptible it is to being fouled by the accumulation of dirt and fiber.
This problem has been addressed in one form by the elimination of fins and relying on conventional tubes as set forth in U.S. patent application Ser. No. 10/421,575, assigned to the assignee of the present application and incorporated herein by reference. A further approach has been to selectively stagger the successive rows of tubes in relation to the direction of airflow as described in U.S. Patent Application No. (PCT/US03/12468), Continuation In Part Application of Provisional Application Ser. No. 60/376,486 filed on Apr. 30, 2002, assigned to the assignee of the present application and incorporated herein by reference.